Détection gaz
L’émission accidentelle ou non contrôlée de gaz peut avoir de lourdes conséquences sur la santé et la sécurité des personnes, sur les biens matériels et sur l’environnement. Le détecteur de gaz joue un rôle important dans la maîtrise des risques d’incendie, d’explosion et d’émission de substances nocives.
Gas detection to combat an invisible enemy
Three types of gas
three different risk
Gas detection consists of continuously analysing the environment for too high (or too low) a concentration of one or more gases for which they have been programmed.
Flammable gase
The release of these gases in excessive quantities can cause fires or explosions. The most common substances in this category are hydrogen (in battery rooms), butane, propane and methane (in rooms with boilers). There are also flammable vapours from solvents and hydrocarbons.
Toxic gase
Exposure to these gases can be harmful even in very low concentrations. Exposure can lead to poisoning or even death. Examples include ammonia (machine rooms for deep-freezing and fertiliser manufacture), hydrogen sulphide (refinery, water treatment) and carbon monoxide (underground car park).
Oxygen level
Although oxygen is a vital gas, it can be harmful or even fatal to humans in too low a concentration, but also in too high a dose. This is known as anoxia and hyperoxia.
Obligations légales, normes et certifications
Installation required by insurance companie
The installation of gas detectors is not compulsory. However, they are required by insurance companies in high-risk areas (see table of applications).
The decision also rests with the head of the establishment, who is responsible for the safety of his or her premises. An accident could cause very serious damage, affecting people’s lives and leading to the destruction of buildings.
ATEX zonin
The ATEX standard governs, at European level, the protection of workers in areas where there is a significant risk of explosion due to the presence of flammable materials. It categorises each zone according to its degree of risk – from 0 (permanent danger) to 2 (rare danger).
Gas detection sensors are installed in zones 1 and 2. They must be ATEX certified.
The level of security integrit
The IEC 61 508 and EN 62061 standards have given rise to SIL (Safety Integrity Level) levels ranging from 1 to 4. These levels are a measure of the performance or reliability of systems with fire safety or gas detection functions.
For gas detection, all sensors must achieve SIL 2 level.
INRS guide
The INRS (Institut national de recherche et de sécurité) has published guides for estimating the specific gas concentration limits for each product and calibrating sensors accordingly. – For flammable gases, we talk about LELs and UELs (Lower and Upper Explosive Limits of these substances). – For toxic gases, we talk about VLE (limit value for exposure over a maximum period of 15 minutes) and VME (average value for exposure over a period of 8 hours).
For oxygen content, the threshold is expressed in %, 21% being the ideal concentration.
Which gas detection solution is right for your business?
Gas detection is particularly well suited to industrial environments. More broadly, it concerns all sectors of activity where there is a permanent residual presence of gas (pharmaceutical laboratories, food processing plants, water and waste treatment sites, etc.).
Each business sector has its own risks associated with uncontrolled gas emissions.
| Applications | Flammable gases | Toxic gases | Oxygen |
|---|---|---|---|
| Boiler room | X | ||
| Battery room | X | ||
| Industrial kitchens | X | ||
| Laboratory | X | X | X |
| Water treatment | X | X | |
| Food industry | X | X | |
| Paint | X | ||
| Pharmaceuticals | X | X | X |
| Waste treatment | X | X | |
| Chemicals & Petrochemicals | X | X | X |
| Metallurgy | X | X | |
| Energy | X | X | |
| Data centre | X | ||
| Refining & Gas | X | X | X |
| Car park | X | X |
Fire and explosion risks associated with gas
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Technology that can cope with any situation
The different types of senso
Sensors continuously analyse the presence of gas in an area according to several criteria: the type of gas to be detected and the level of concentration.
There are different technologies, each associated with the detection of a specific gas. A sensor can be equipped with one or more of these technologies:
- Catalytic (combustible gases)
- Electrochemical (toxic gases)
- Semiconductor (toxic and oxidising gases)
- Infrared (CO2, sulphur dioxide and methane)
- PID (toxic gases)
- Thermal conductivity (hydrogen and helium)
- Ionising radiation (radioactive gases)
Calibration bottl
The calibration bottle is used when the sensors are commissioned and then during maintenance, to calibrate the detectors so that they are perfectly matched to the concentration (% LEL measurement) and the gas to be detected.
The power statio
Gas detectors are connected to a control unit. The control unit may be specific to gas detection or the SSI fire safety control unit.
A gas detection system can manage up to 2,500 detection points, depending on the needs of the site to be monitored (1 or 2 points for a small boiler room, around thirty for a pharmaceutical laboratory, up to several hundred for a refinery) .
It activates the alarm in the event of abnormal concentrations and triggers the safety procedure.
3 essential installation stages
Given the many types of gaseous agents and the specific characteristics of each, installing a gas detection system requires a precise methodology that can be summarised in three stages.
Risk analysis and technical proposal
- Risk study (gases involved, ATEX zoning, definition of flash point, etc.). Analysis of the environment. Definition of the technology and equipment to be used.
Installation
- Position the sensors, taking into account the correct height for the type of substance to be analysed (on the floor, at ground level, on the ceiling). Set up the sensors to the recommended levels using the calibration bottle. Commissioning and checking of safety devices (shutdown, gas valve, low voltage cut-off, audible and visual alarms, alarm forwarding, etc.) ….
Maintenance
- Each operator is responsible for defining the frequency of maintenance and calibration of the detectors in accordance with the manufacturer’s instructions: every year for flammable gas sensors, at least every six months for toxic gases. Change detectors according to the level of gas in the atmosphere, which can damage the sensors.
Entreprises DEF and Oggioni, your DEF Network experts in gas detectio
DEF (France) and Oggioni (Italy) can advise you on the best solutions for your situation and guarantee compliant installation.
As a manufacturer-designer for nearly 30 years, Oggioni has a comprehensive range of solutions. The diversity of our products means we can adapt to all industrial and regulatory requirements. The products comply with ATEX requirements and are SIL 2 certified.
With its dual expertise in fire and gas, DEF has been meeting your fire safety and gas needs for over 60 years. The gas detectors can be connected to the company’s own fire and gas detector control units, as well as to SSI fire safety control units.
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